Temporal range: Late Triassic, 230 Ma
Fossilized remains of Silesaurus have been found in the Keuper Claystone in Krasiejów near Opole, Silesia, Poland, which is also the origin of its name. The type species, Silesaurus opolensis, was described by Jerzy Dzik in 2003. It is known from some 20 skeletons, making it one of the best-represented of the early dinosauriformes.
Silesaurus measured approximately 2.3 meters (7.5 feet) long, and was facultatively bipedal. It was light and built for speed.
Scientists think that Silesaurus was not a dinosaur, but rather a dinosauriform. Dinosaurian features lacking in Silesaurus include an enlarged deltopectoral crest (a muscle attachment on the humerus), and epipophyses (enlarged tendon attachment above the postzygapophysis) on the cervical vertebrae.
However, Silesaurus has some dinosaurian characteristics as well:
- a brevis shelf (a bone surface on the ilium that functions as an attachment site for tail muscles)
- ischium with a slender shaft
- femur with a reduced tuberosity that borders the ligament of the femoral head
- a prominent lesser trochanter
- an overlap of the ascending process of the astragalus with the tibia
- a concave proximal articular surface for the reception of the distal end of the fibula on the calcaneum
- Dzik, J. (2003). "A beaked herbivorous archosaur with dinosaur affinities from the early Late Triassic of Poland." Journal of Vertebrate Paleontology, 23(3): 556-574.
- Nesbitt, 2011. The early evolution of archosaurs: Relationships and the origin of major clades. Bulletin of the American Museum of Natural History. 352, 292 pp.